


I'll Never Leave You

by kickcows



Category: Haikyuu!!
Genre: Feels and Smut, M/M, Plot What Plot/Porn Without Plot, Secret Relationship, Twincest
Language: English
Status: Completed
Published: 2021-01-23
Updated: 2021-01-23
Packaged: 2021-03-15 01:40:01
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 4,123
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/28930395
Author URL: https://archiveofourown.org/users/kickcows/pseuds/kickcows
Summary: Atsumu gets dumped, and Osamu is there to help pick up the pieces of his twin brother’s shattered heart, hopefully without damaging his own in the process.
Relationships: Miya Atsumu/Miya Osamu
Comments: 6
Kudos: 182





	I'll Never Leave You

**Author's Note:**

> This is a gift fic for a very dear friend of mine. She wanted some Miya twincest, so I'm here to deliver that. :) Please enjoy!

* * *

For years, Osamu has watched his twin brother go through heartbreak after heartbreak. Sometimes Atsumu was the one doing the breaking of hearts, but for the most part it was his brother that was the victim of no longer being loved and or wanted by the party he’d been dating. Female, male - it didn’t matter. Atsumu had been known to be a Lothario towards both sexes, while Osamu stayed quiet and didn’t really say much to anyone else. There was no need to, as he wasn’t anywhere near as loud and boisterous as Atsumu - all eyes were on him. On and off the volleyball court, which suited Osamu just fine. 

Atsumu was currently going through a more difficult breakup, as he’d been dating this girl for almost four months - a record for him. Osamu only got to spend time with him when they had practice before and after school - any other time, and Atsumu was off with his girlfriend, leaving Osamu alone. Again - it was fine; he was used to this as it had been this way since they started junior high. 

After dinner, Osamu had cleaned up the kitchen and started to head to his bedroom when he heard the distinct sound of his brother crying. Knowing that he really didn’t have any choice, he turned and went back to the kitchen. Sitting down next to Atsumu, he turned towards him and put his arms around him. It was exactly what his brother needed, as Atsumu clung to him and started to really wail as he hugged him as best he could sitting sideways on the chair. Keeping quiet, he waited for Atsumu to start talking, which he knew would happen at any moment as his brother was fond of filling the silence with his own voice. 

“What’s wrong with me, ‘Samu?” Atsumu hiccuped next to his ear, the sobs beginning to slow down. “There must be something wrong with me. I thought we were happy!” 

“Sometimes it’s easy to fake.” Osamu had watched Atsumu and his girlfriend often at school, and had seen the signs of her starting to fall out of teenage love with his brother. But if he’d said anything to Atsumu, he would have been reprimanded by Atsumu and told that he was just jealous. There was never any winning with him. “She wasn’t good enough for you, ‘Tsumu.” 

“It seems like no one is good enough for me.” His brother started to cry again, his head hitting Osamu’s shoulder with a dramatic _thunk_. “I’m going to be alone forever.” 

His hands curled into the fabric of Atsumu’s shirt, his heart beginning to beat faster as his brain was trying to convince him to say something that would alter their relationship in a way that Osamu wasn’t sure he was ready for. If he told Atsumu his true feelings - feelings he’d discovered at the beginning of their tenure in high school - then it would ruin everything. There was no reason to do that, but his brain was trying to tell him that maybe now would be a good time to show his brother that that wasn’t the case. 

A long time ago, when they had been kids, they had been extremely close with one another. So close that they would sleep with their arms around each other, holding each other tight to keep the nightmares away. That all stopped when they started junior high, and moved into separate bedrooms. Osamu had been _miserable_ after that separation, but his brother had not. It seemed that Atsumu was happier without him around, which he’d learned to deal with. His own heart began to pine for his brother in a way that he knew was bad - he shouldn’t have _those_ kinds of feelings for Atsumu, because that was wrong. Osamu kept those secrets to himself, and while he spent time playing volleyball with his brother, he ignored the part of his brain that was showing him how much his brother loved him. But it wasn’t in the way that he really wanted it to be. 

He would never leave Atsumu. Never. They might fight, and say stupid things to each other, but Osamu knew that he would always be there for his brother at a moment’s notice. Swallowing, he kept his eyes closed as he decided maybe his brain was right - now might be the best time to tell his brother how he really feels about him. “You have me.” He said, hoping that it didn’t sound as lame to Atsumu as it sounded in his own ears. 

“Of course I have you, but that isn’t what I’m talking about!” Atsumu groaned, shaking his head back and forth against his shoulder. “I’m talking about dating someone who actually likes me!” 

“You’re not listening.” Osamu felt his stomach twist into knots as he tried to keep his calm. “You have me.” 

That got his brother to lift his head up and look him in the eyes. “What?” 

“I’m not going to leave you. I’m not going to abandon you.” His hand trembled as he brought it up to Atsumu’s face, his ears beginning to ring as the blood rushed up to his head. “The people you date? They’re stupid if they can’t see how great you are. But I can. I know you’re amazing.” 

“You _have_ to say that because you’re my brother.” He was shocked when he felt Atsumu turn his head towards his hand, his brother’s breath now touching the back of his hand as Atsumu rubbed his face against his palm. “That’s not really a fair statement either, ‘Samu.” 

Knowing that his brother would not listen to him no matter _what_ he said, Osamu decided that maybe it would be better to show him without words. Anchoring his thumb to Atsumu’s cheek, Osamu moved his head towards his brother’s and let his lips touch his with the barest hint of a kiss. He felt Atsumu jerk, but then he returned his lips to his brother’s, kissing him with more confidence. Atsumu’s lips didn’t do anything at first, but then….then the dam broke and Osamu’s world changed instantly. 

Atsumu began to kiss him back, the two of them now standing up next to the table, their arms winding around each other’s bodies while their lips stayed locked together. Osamu opened his mouth, and before he could push his tongue into Atsumu’s mouth, he felt his brother do it first. Groaning low, he welcomed the touch of his tongue against his own, his fingers clutching tight to Atsumu’s shirt again, willing his brain to accept that this was real - this was happening. It wasn’t him living out some fantasy in his bedroom while jerking himself off. No, Atsumu was kissing him with an equal amount of enthusiasm, if not more than him. 

Breaking off the kiss, Osamu stared into his brother’s eyes, both of them breathing heavily as they stared at one another. “Now do you get it?” Osamu asked, hoping that he wasn’t about to get slapped by his brother for doing the unthinkable. “I won’t leave you.” He whispered, keeping his gaze locked with Atsumu’s eyes. “We could do things together.” 

“What kinds of things?” 

“All kinds of things.” Pulling his arms away from Atsumu, he put a hand on Atsumu’s chest. He could feel how fast his heart was beating, thankful that he wasn’t the only one having a rapid heartbeat right now. “We could kiss like we just did. We could touch each other where we’re not supposed to. We could kiss each other in places where we shouldn’t.” His vision was becoming spotty as he tried to calm down his racing heart. “We could have sex.” 

“Right now??” Atsumu asked, the eagerness apparent in his voice. “Can we do that right now?” 

He nodded his head, and before he could say anything else, Atsumu was dragging him to his bedroom. The door opened, then slammed closed, and then Osamu felt his back pressed up against the door as his brother’s mouth returned to his, the two of them sharing a kiss like they hadn’t seen each other in months. Osamu moaned, putting his arms around Atsumu’s neck as he felt his brother’s tongue push back into his mouth, the two of them returning to those intense kisses that they’d shared before out in the dining room. 

Atsumu pushed his groin against his own, making Osamu break away from the kiss with a keening moan leaving his throat at what he felt there. “‘Tsumu…” He moaned his brother’s nickname, pushing his hips forward as Atsumu returned the push with an equal amount of enthusiasm. “Nnngh…” 

“Are you sure about this, ‘Samu?” Lips began to leave kisses on his neck, sending shivers down Osamu’s body as he clung to his brother for dear life. Teeth dragged against the taut skin, and then a little nip made his knees buckle. But before he could fall, Atsumu was holding him in his arms, returning his lips to his as they kissed each other again and again. “I never really thought about you like this.” 

“I-It’s okay.” Osamu tried to remain calm, as he felt his brother’s hands slide down to his ass. When he felt him grab a handful of both cheeks, he released another desperate moan. “‘Tsumu, please…” He wasn’t above begging, and while it wasn’t something he wanted to do, he would do it to make his brother see just how bad he wanted him right now. 

The warmth against his own body disappeared as Atsumu moved further into his bedroom, Osamu left standing against the door, trying to catch his breath. He looked at his brother and watched him untie the knot of his drawstring, Atsumu taking his time to get his shorts off. Once they dropped to the floor, Osamu’s eyes traveled down to look at his cock and saw that it was as hard as his was, with the tip glistening a bit. He rushed towards where Atsumu was standing, much like he would to receive a ball in play, and dropped down to his knees so that he could be up close and personal with his brother’s cock. His lips gravitated towards the tip, Osamu closing his eyes as he moved it back and forth over the weeping slit. 

Strong hands touched his hair, and kept him in place as Atsumu slowly fed Osamu his cock. Moaning low, he let the thick flesh slip between his lips and onto his waiting tongue, his mouth filling with saliva as he waited for Atsumu to be fully inside of his mouth. The tip of his nose pushed against the dark curls at the base of his brother’s cock, Osamu taking a deep breath of the rich scent that came off of Atsumu’s body. The musk stung his nostrils, tears springing to his eyes as he felt the tip of Atsumu’s cock start to nudge the back of his throat. He gagged, and then recovered as spit spilled past his lips, his throat now welcoming the thickness of his brother’s cock. 

He bobbed his head slow, not at all that experienced when it came to these sorts of things. He’d dated girls in the past, but had never gotten that far with any of them - definitely not far enough to have them suck his own cock. So he was doing to his brother what he figured he would like, and since they were twins, he had a pretty good feeling that what he was doing was good. It also helped that Atsumu was moaning like crazy now, as he kept sliding his lips up and down the length of his cock, his tongue caressing the stiff flesh before swallowing it back down his throat. 

“‘Samu…” His brother’s breathless voice made his own brain stop working for a second as this sounded better than his wildest fantasies. He tried to hold onto that sound, repeating it over and over in his head as he carefully put his hand on Atsumu’s balls, giving them a good squeeze at the same time he began to deepthroat his cock. “Oh shit oh shit oh shit oh shit...S-Stop!” 

Refusing to listen, Osamu kept his mouth secure around Atsumu’s cock, sucking on him like his life depended on it. The fingers in his hair yanked hard, the tears returning to his eyes as the initial pain hit him, but as he opened his eyes to look up at his brother, he saw that Atsumu was staring down at him with a look in his eyes that made his own cock drip. He gave a nod of his head, then closed his eyes again as he really went to work on Atsumu’s cock. Twenty seconds later, he tasted his brother’s spunk for the first time, the thick fluid pouring down his throat as he felt Atsumu’s cock twitch against his tongue. He swallowed his load, the rich sweetness almost too sweet - stupid sweets that Atsumu loved to snack on - but Osamu knew that it was a taste he was going to want again and again. And from the sounds that Atsumu was making, he had a feeling that it was going to be the same for him. 

“Well?” Osamu sat back on his heels, after carefully licking up the rest of the mess off of Atsumu’s cock as he stared up at him, eyes somewhat glassy. “Good?” 

“How many dicks have you sucked?” 

“None.” 

“Bullshit.” 

“I’m not lying.” Osamu shook his head, as he watched his brother sit down on the edge of the bed. “Why? Was it that bad?” 

“That was the best blowjob I’ve ever received.” The grin on Atsumu’s face had Osamu’s stomach rolling. The bitter tang of his brother’s cum still clung to the roof of his mouth, but it was tolerable. “You’re really good, ‘Samu.” 

“Thanks.” _I think_. Standing up, he walked over to the bed, and saw Atsumu’s cheeks were now slightly pink. “Do you want to stop here? Or do you want to keep going?” 

“What are you suggesting?” 

“Sex.” 

Atsumu’s eyebrows raised up. “Am I taking you?? Or would you take me??” 

“It doesn’t matter to me.” It really didn’t. He didn’t care one way or the other - he was about to lose his virginity to his brother by either method. “You’re the one that’s been in relationships and have had sex.” 

“I haven’t had sex, ‘Samu.” 

His hand faltered at that comment, surprised by his brother’s admission. “What?” 

“It’s probably why I just got dumped.” Atsumu shook his head. “She really wanted to, and kept telling me it would be safe, but I just couldn’t do it. Something was holding me back.” 

Osamu didn’t know what to do with this information. “You’re still a virgin?” 

“Yep.” Atsumu was now laying down on the bed, his shirt gone. “Hey - your clothes are still on, ‘Samu. Take them off.” 

_Right. Clothes_. He was still wearing them, wasn’t he? Getting them off proved to be a pain, as he was harder than all hell right now. He got them all off, and sat next to Atsumu, whose hand was now touching his cock with tentative touches. “You can really touch it if you want.” He whispered, the room suddenly feeling really cold as the heat of Atsumu’s palm felt so pronounced against his cock. 

“You look like you’re about to pop.” His brother rubbed the pad of his thumb over the tip, spreading some of the precum that was constantly dripping from the slit. “Do you want me to make you come like this?” 

Osamu’s eyes were closed, his breathing becoming more and more labored as Atsumu’s hand stroked his cock. “D-Do whatever you want.” It was a struggle to get the words out, his own thighs spreading apart as he felt Atsumu’s fingers slipping down to cup his balls. “I’m so close, ‘Tsumu…” 

“Show me what you look like when you come, Osamu.” 

Heat rushed through him fast as he began to come, the way Atsumu said his full name pushing him right over the edge. It was embarrassing, the noises he made sounded desperate and whiny, but it felt so good to come - and Atsumu’s hand kept pumping him through the orgasm, jizz covering his brother’s stomach. He groaned as he watched Atsumu pick some up with his fingers, and took a few long licks with his own tongue. 

“You taste real nice.” Atsumu grinned, Osamu releasing a breathless laugh at the stupid comment his brother had just made. “I want you to fuck me. Would you do that?” 

For someone that always liked to be the center of attention, Osamu was surprised to hear his brother request that, but couldn’t say no. “Lube?” 

“Drawer.” 

Turning to the left, he opened the nightstand drawer and saw a few different lubes, and saw a dildo that was quite impressive. He smirked, then picked one of the bottles up and began to pour some of the liquid onto his fingers. “Where’d you get a toy like that?” 

“Shut up.” The blush returned to his brother’s cheeks, as he began to slowly touch his puckering hole, Osamu gently coaxing it to open up for him with smooth, gentle touches. “Internet, duh.” 

“Smart.” He got one finger inside of his brother, and saw him shudder as he slowly pushed it into his body. “This should be no problem for you, then.” 

“H-Haven’t used it...in a while…” Atsumu grabbed onto the bed, his chest arching up as Osamu began to push a second finger into his body. “Nnngh….S-Samu…” 

“Relax.” Osamu began to pump his fingers carefully, alternating between spreading them open and just using them to fuck his brother open. “If you don’t relax, this is gonna hurt so much more than it has to.” 

“Did it hurt when you had sex the first time?” 

“Idiot - I haven’t had sex either.” He mumbled, feeling somewhat shy at admitting that to Atsumu. “Now, stop distracting me.” 

Getting three fingers in Atsumu took a little bit of time, but once he did, he kept his eyes on his brother’s face, loving how the expression would change whenever he managed to nudge against his prostate. “T-Take them out….I want you…” 

“I want you too, ‘Tsumu.” Osamu pulled his fingers out, and saw his hole stay spread open for him. Grabbing the bottle of lube, he poured more onto his hand and began to stroke his own cock, transferring the liquid to his stiff flesh. Kneeling between his brother’s legs, he let the tip of his cock rest against his spread hole. “Atsumu - look at me.” He waited for his brother’s eyes to focus on him, and once their eyes were locked, he slowly began to push his cock into his body. He groaned low as Atsumu’s inner walls spasmed around him, trying to push him back out but he wouldn’t let that happen. “A-Atsumu…” 

His hands dropped to the sides of Atsumu’s face, just above his shoulders, his head dropping down as the warmth that surrounded his cock became almost overwhelming to his senses. He had to stop moving, or he was going to explode again. Luckily, his brother didn’t tease him and instead brought his lips to his, kissing him to distract him. He welcomed it with a groan, his hips moving slightly forward as they started to kiss one another. The slight slip had him groaning again as he felt Atsumu’s walls cling tight to his cock, his own body responding to the tightness by throbbing a little. 

“S-Stop.” He groaned, resting his head against Atsumu’s forehead as he tried to get his body to calm down. “I can feel that!” 

Atsumu was not listening to him. He could feel him squeezing tight around his cock, his body growing hotter by the second. “Sorry…” 

“No, you’re not.” 

They shared a grin, Osamu surprised by how good this felt. It should feel awful - it should feel terrible and bad, but it didn’t. It felt incredibly good, and now that he had passed that first wave of possible explosion, he began to roll his hips slow. The pace was easy to set, as he felt Atsumu wrap one leg around his waist, their chests pressed together as both of their arms held onto each other in an embrace. He could feel Atsumu’s cock rubbing against their stomachs, his hips moving a little faster to get some good friction going on his brother’s cock. It didn’t take very long before he felt Atsumu’s body tighten up around his cock in a way that was different, and then he heard his brother moan his name as wet heat began to spread against their stomachs. Osamu pushed his hips forward again, trying to push past the squeezing that Atsumu’s body was doing. That extra tightness he encountered was enough to push him over the edge again, coming deep inside of his brother with a low moan. 

It took him a few minutes to return back from his orgasm, and when he did, he saw Atsumu was looking up at him with a smile on his face. “What?” 

“That was amazing, ‘Samu. Can we do it again?” 

“Right now?” He asked, even though his cock was already becoming soft. It slipped out of Atsumu’s body, the both of them releasing a soft grunt at the loss of connection. “Might have to wait a few.” 

“I don’t mind.” Atsumu’s hand touched his face, then pulled him down to kiss his lips. “I love you, ‘Samu.” 

“I love you too.” He returned, kissing him again and again. 

Thirty minutes was all he needed to recharge, and they were going back at it, this time with Atsumu on his hands and knees, Osamu taking him from behind. He brought his brother to an orgasm with his hand while he pounded his cock hard into his body, the position giving him a lot more leverage than the other position to do as such. Hearing Atsumu scream for him, the sounds muffled by the bedding as his brother’s head had been planted on it after he’d brought him to an orgasm, was the best reality for Osamu. He snapped his hips a few more times, then poured his orgasm into his brother’s ass for the second time that night. 

Wanting to clean up, Osamu took a shower with Atsumu in their shared bathroom, his own bedroom on the other side. After they got finished in the shower, he started to head towards his own room when he felt Atsumu’s hand touch his shoulder. “Stay with me tonight, ‘Samu?” 

“Is that what you want?” Atsumu was the reason they had separate bedrooms now - Osamu would have been happy to share a bedroom with him for as long as he wanted. Hearing his brother say he wanted him to sleep with him again really did a number on his heart. 

“Please.” Atsumu nodded his head. “We don’t have to have sex again. I just wanna sleep with you.” 

Osamu nodded, then followed Atsumu back into his bedroom. They got under the covers together, Osamu finding the position he used to like sleeping in with his brother. They had both grown a lot since the last time they’d slept together, but they still fit together like two perfect puzzle pieces. He had his head tucked up under Atsumu’s chin, and felt his arms around his body, encasing him in warmth. He fell asleep easily, happy to be back in his twin brother’s arms. 

In the morning, they got ready for school and acted as if nothing had happened the night before. Osamu was okay with this, as he knew that this was a secret that could never be shared with anyone. As they walked to school together, Atsumu turned to look at him. 

“You meant what you said, yeah? You’re never gonna leave me?” 

“Never.” Osamu spoke with a passion that he hoped his brother would understand, as there were people around them now that could hear their conversation. 

“You busy after practice? I could use a little help studying in my room.” Atsumu winked, which made a blush appear on Osamu’s cheeks. 

Before he could answer, they were joined by Aran, who filled them in on some drama that had gone down after they’d left practice the day before. Osamu gave a nod when he saw Atsumu looking at him, the two sharing another smile. He meant what he said - he would never leave him. And it seemed that that made his brother happy to know. Only time would tell where they would go with this newfound facet to their relationship. For once, Osamu was looking forward to the future. 


End file.
